While he does not say so explicitly, Zuckerberg is clearly referring to the reports of widespread surveillance undertaken by the National Security Agency.

Zuckerberg, 29, who has built the world's most successful social network, writes that the Internet works because companies like Facebook strive to make it secure. He adds:

"We work together to create this secure environment and make our shared space even better for the world.

"This is why I've been so confused and frustrated by the repeated reports of the behavior of the US government. When our engineers work tirelessly to improve security, we imagine we're protecting you against criminals, not our own government.

"The US government should be the champion for the internet, not a threat. They need to be much more transparent about what they're doing, or otherwise people will believe the worst.

"I've called President Obama to express my frustration over the damage the government is creating for all of our future. Unfortunately, it seems like it will take a very long time for true full reform."